Block-signal system.



L. A. HAWKINS.

BL'OC'K SIGNAL SYSTEM.

APPLICATION FILED AUG.6. 1906- 1,157,104. Patented 0011111915.

2 SHEETS-SHEET 1.

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Laurence M'lawkifis L. A. HAWKINS.

BLOCK SIGNAL SYSTEM.

APPLICATION FILED Aue.6. I906.

Patented 0ct.19,1915.

2 SHEETSSHEET 2.

Wiffisses hwanfir Laurenw AHcIwkIns o v I WEED snares rarenr carr AURENCE A. nawnms, or sonnnnc'ranr, NEW YORK, assreuon, BY MESNE Assicru- IVIENTS, TO THE UNION SWITCH SYLVANIA.

Application filed August recs. Serial no. 329,347.

' To all whom it may concern:

. current.

street railway practice.

In the practice of my invention Iprov1de,-

Be it known that I, LAURENCE Iii/HAW- Kim's, a citizen of the United States,resid.' ing at Schenectady, county of Schenectady, State of New York, have lnvented certain new and useful Improvements in Block- Signal Systems, of which the following is a specification- My invention relates to block signal. systems for electric railways, and its object is to provide a safe and eflicientsystem pos-r sessing certain advantages not heretofore obtalned. 1

In block signal systems for electricallyoperated railways it is desirable to use the rails not only for the signal circuits, but also as a return conductor for the power- Various arrangements have been proposed heretofore for permitting therails to perform both functions. Since it has heretofore been considered necessary that each block circuit should be insulated from the adjacent blocks, as far as the signal current is concerned, numerous devices, such as choke-coils, inductive bonds, and special arrangements of connections, have been devised to transmit the powercurrent from one block to another, While preventing the fiovv of the alternating current employed for the signal circuits. All of these' devices are expensive and inefficient, since they must furnish sufficient reactance to prevent the flow of signal current from block to block and at the same tinie'transmit the powercurrent Wi'tllGdt, saturating the magnetic circuit of the devices.

()ne object of my invention is the arrangeinent of the signal circuits so that the rails may be made continuous, as ln an electric railway not employing block signals.

blocks are done away with, and therails may be'bonded or elded as in combination with arailway having both rails conductively continuous tori-all. currents, signals for the blocks, controlling c rcuits therefor, sources of alternating current connected across the rails at intervals, track relays supplied With current. from the I In Fig.1, A represents the two rails of the 1 preventing the operation of each relay ex- BLOCK-SIGNAL srsrnivif y my invention the insulating joints between in the usual,

AND SIGNAL COMEANYfA GORPQRATION OF PENN- a'oct ie, i915.

cept by current from one of said sources,

only, this means, inthe arrangement illustrated in "the drawing, consisting of a second inding on the relay cooperating With'the track Winding to produce the relay torque and supplied with current of a character to produce a torque in the relay only When the track inding is supplied With current from the propersource. r v

In the embodiinentof my invention which I' have disclosed herein I employ for. the

c5 track-circuits a plurality of sources of our r'entdifiering in character from thepoWer-- 1 current and from each other connected tothe- .tr'2 tcl -rails at intervals corresponding to 'the length of a block and employ for the difterent blocksrelays responsive to current of one character but not tothat of another. By

means of thiscombination the relays maybe arranged to-operate in the same manner as though the several blocks Were ;Wh0lly insulated from each other.; V V

. In arranging the' several parts of thesystern in its preferred form my invention further comprises certainrelative arrange ments of current sources andrelays. Broadly stated, I connect the sources of current across the rails at lntervals and group the relays in pairs placed between each tWo adjacent sources and connect the relay contacts so that each relay'controls the signal guardingthe portion of track between therelayand Jone.

adjacent source, Each-portion of track be-.

it and -one adjacent sourcewand the. other relay by a car at any point between it and the other adjacent source. In this preferred I form of thesystem, each signallis preferably controlled by; tWorelays. ,My lnvention Will be better understood from a consideration of thefollovving decompanying dra vinglsfln which- 7 p igure 1 's a diagram] "llustrating my I I scription taken in connection Wltlt the sac invention in its simplest forms and Fig. 2

illustrates the arrangement which I preferto track, hich are both continuous, as in the usual street railway practice, so as to form a return-conductor for the power-current. B represents the supply conductor for the power-current, such as a third-rail or trolley Wire, which is connected to one terminal of the source of power-current indicated at C. The other terminal of the source may be connected to the track-rails A through a differential choke-coil c. lhe generator C may supply any suitable kind of power-current such as direct-current or low-frequency alternating-current. D D and D represent alternating current generators, preferably of high frequency; the current delivered by the three generators being of difierent frequency. d, d d and (5 represent supply-conductors from these generators extending along the track. Conductor (Z is a common return-conductor for all these frequencies. E E etc., represent transformers which have their primaries connected to the supply-conductors and their secondaries connected across the track-rail. It Will be noticed that adjacent transformers are connected to supply-conductors of different frequencies, tnat is, the transformer E supplies to the rails a current of the he quency delivered by the generator D While the transformer E delivers current of the frequency of generator D The transfornr ers are preferably arranged With an 'airgap in the magnetic circuit, as indicated, in order to prevent saturation by the flow of power-current, such as might arise from defective bonding. A small ohmic resistance e may also be inserted in the secondary of the circuit of the transformers, in order to keep down the flovv of power-current. sistance e, and also the air-gaps in the magnetic circuit of the transformer, serve to prevent the transformer from giving too heavy a current when short-circuited by a I train standing directly across the secondary terminals. lhe distance between adjacent transformers corresponds to the desired length of a block. Relays F F etc., are

connected across the rails at the entrance of theseveral blocks. These relays are each arranged to respond to only one frequency, and for this purpose are provided With tWo cooperating Windings,one connected across the rails and the other supplied independently of the rail-circuit with current from the supply conductors. I have shown the relays as of the type having one fixed and one movable coil, but it will be understood that the illustration is purely diagrammatic, and that any other form of selective relay may be used. The stationaryivinding of the relay F is shown connected across the supply-conductors (Z and (Z so that although its movable or track-coil is traversed bv current from each of the transformers rent delivered by the transformers E The This re- .relay F similarly responds to the current 'Which has just entered the portion of tract:

between-the transformers LE and E.

It Will be perceived that since the rails are continuous, a portion of the current from each source will pass beyond the block and through other signaling devices so that not only is there a certain waste due to this lealage-current, but also each relay must be a suflicient distance from every source of current of the character to which it re sponds, except the source from which its current properly comes, to prevent its being actuated from any other source. Steel rails, however, ofier a comparatively high impedance to high-frequency alternating-currents, and by employing such currents for the signal circuits I am enabled both to re duce the leakage-current to a reasonable amount, and also to reduce the kinds of current employed to a small number. It Will be further seen that the length of a block is not absolutely determinate as in the ordinary arrangement, since the rails are continuous and the shunting as a train approaches a relay is gradual. In my system a signal for one block is set at danger a short time before the signal for the preceding block has cleared. In other Words there is an over-lap Which is, to a certain extent, indeterminate. I have found, however, that by the use of a ugh-frequency signal-current, so as to obtain a high rail-impedance,

and by the proper proportioning of the signal devices, the over-lap may be made so short and so definite as to be practically negligible.

With the above explanation in mind, the

operation of the system shown in 1 will be clear. With the car H in the position shown, the rails between the transformer and relay F are short-circuited. Consequently, track-coil of relay F is deenergized so as to open the circuit of signal. a and allow the signal to go to danger. This signal Will obviously remain at danger as long as the car is between transformer and relay F ,-that is as long as the car is in the block guarded by the signal. ll hen the car approaches the relay F it gradually shunts the current from this relay until, When a certain point is reached, the voltage across relay F Will be lowered to such i .57, liQli an' amount asto put the signal G at dangeia. The signal Gr? consequentlygoes to danger sometime before the carenters'the block between relay F and transformer E and this signal, in accordance. with the usual practice, which arranges the signal at such' a point thatit will notgo to danger until the locomotive has-passed, should be placed a certain distance'in frontof theQrelayF This d stance forms the over-lap over the system; That is, whilethe train is Wltlllil this distance both signals G and G will stand at danger. The length of this overlap obviously depends upon the impedance of.v

- 'theyrail-circuit as comparedtofthe impedsince ofthe relay-circuit, and the regulat on of the transformer supplying jthe relay,

Even: with the arrangement shown in Fig. 1, this over-lap may be sufficiently short and determinate for commercial purposes, and

with improved arrangements, such as will be hereinafterdescribed, theover-lap; may be made exceedingly short and definite; that is, less than'one hundred yards.

it will be'seen that the transformers E and E", which are the nearest-transformers connectedto the same supply-conductors, are

oppositely connected so as to impress onthe track voltagesone hundred and eighty de grees out ofphase. Thepurpose of-this-connection is to increase the safety .of the sys f With this connection, whatever curtem. rentfrom transformer E reaches relay. F will tend to put it at danger instead of holding it at clear position. The nearest trans:

former, other than transformer E which can supply current to relay F of the proper frequency and. phase to move to clear posi.

tion, is three blocks from transformer 13 that is, five blocks away from relay F Consequently no appreciable amount of effective current can possiblyreach relay F}.

from any source except its own transformer.

It will furthermore be noted that the central] point of the block between transformer E and relay F is equi-potential with respect to transformers E and E when oppositely connected, as shown., Consequently, atrain in the middle of this block will have no effeet on the relay F and beginsto shunt it The reverse connection oftransformers E and.

only after passing the central point.

The simple arrangement. described Fig. '1.-has certain disadvantages. -In the first place, itjwill be seen that relay F iscon-v nected directly in shuntzto transformer E while it is, a block away from transformer E Consequently, this relay is traversed by ax useless current, which is larger than the useful current whlchflows through it. In the second place, asatra n approaches a relayiand begins to shunt it, thefiincreased current flowing from the transformer, ,produces [an increased drop Eon the rails between the transformer. and relay, so

that the fall of current in th'e, .relay, is".

greater and thefover-l'ap is longer than would be the case, if. the fall" impedance of a: whole block were not between the transef. former and the approaching train. In the third place, at least three different lrinds of current must be employed for the-signal circuits. These. 'objections, vwhiienot affecting the operativeness ofthe system, decrease its" commercial, iciency, and may all :be re moved byfthefmodified arrangement shown in. Fig. 2., lnthis arrangement twoi relays are employed for each nected at the-center of the block; the-two relays in each pair-responding respectively to the currents front the two transformers at' I the ends of; the block. The two relays are arranged olntly to control the signal for the a block, .as by having-their armatl Ire contacts block, and "area-icon V V placed "in series with each other iin :the sig-.

na l-circuit. The track-coils of, the relays may be, connected in any suitable manner, for example in parallel as shown in the bigure. "In Fig. 2 onlytwo different frequem cies D and D are employed- The. operation-of the system is as followst I with the car H in the positionshown, the

rails between transformer E and relay F are short-circuited so that thistransformer can supply'no current to this-relay .The

current from the transformer E has no effect on the relay Ff, sothatthis'relay is de'elnergized'and drops its armature, as shown, moving signalGr to danger. As the train H proceeds in thedirection of the arrow, it'

gradually shunts the current supplied by:

Con

transformer E around the relays. sequently, at some pointfjbefore the train reaches the relays,]relay1F will also have dropped its armature, therebymaking a secc nd break in the signal-operating mechanism G Obviously, relay F can not again pick up its armature until after the train has passed a certain distance tothe other side of transformer E3. As the train ape preaches transformer E however, it draws; from the transformer continually larger;

current, which reduces the potential irn-Qfi pressed by thls transformer on the track,

and consequently. reduces the amount of curr t supplied by this transformer to rel y Ft. For instance, 1f the relay F is designed so as to drop its armaturewhen the voltage across the terminals is reduced to one-fourth its normal value, the signal G will go to danger when the train reachesa point near enough to the transformer E to cause it to give a sufiicient current to lower the voltage impressed by it on the track to one-fourth its normal value. The distance of this point from the transformer will obviously depend,

first upon the impedance of the traclcrails,

, stance, as three hundred cycles, so as to give a high impedance to the rails, the relay and transformer may readily be designed so that the relay will not drop out until the train is' within less than one hundred yards of the transformer. This one hundred yards or less, forms the overlap of the system, since when the train is this distance from the transformer if, the signal G will go'to dan- V ger on account of relay 1* letting go its armature. Signal G is meanwhile still at danger, since, although relay F will by this time have picked up its armature, relay F will still be in open-circuit position, as the train is between this relay and the transformer E which supplies it. Thus both signals G and G are at danger While the train is passing transformer E Belay F will not pick up its armature until the train has passed transformer E a sufficient distance to allow the voltage supplied by transformer E to the track to rise a sufficient amount for this purpose.

The signal G should, in accordance with the usual practice, be placed sufficiently far back of transformer E 'so that it will not go to danger until after the locomotive has passed it. As stated above, this distance may be not more than one hundred yards, and since the signal is sure to go to danger before the train is directly over the terminals of transformer E there is no chance that the train can have passed the signal any distance with the signal still at clear. In other words, the indeterminateness of the over-lap may be made so slight by the proper design as to be negligible.

The location of the transformers at the en-- trances to the blocks and the relays at points beyond, so that an approaching train reaches the transformer first, assists materially in making the over-lap short and definite, for the reasons alreadyexplained. I

The only source of variation in the length of this overlap is variation of impedance in the rails. The power-factor of the rail-circuit at a high frequency is comparatively low, and the power-factor of the secondarycircuit of the supply transformers is preferably made practically the same, so that 'Variation in the length of track included in tain distance beyond the next transformer.

Also a broken rail anywhere between the two transformers wlll put the slgnal at danger,

since it will cut ofi current of one frequency from the relays, so as to deenergize one of them.

It will be seen that the current from the secondary of each transformer divides, part passing in each direction. On reaching the relays, part of the current passes through the relays and part tends to pass beyond the relays and to return through the other signal devices connected across the rails beyond the relays. If, however, the impedance of the'relay-circuit from rail to rail is made small compared to the impedance of the rails of a block, the amount of current which passes beyond the relays will be comparatively small. Furthermore, it will be noticed that in Fig. 2, the adjacent transformers which are connected to supply-conductors of the same frequency, such, for instance, as transformers 'E and E are oppositely connected, in the same manner as in Fig. 1, so

that any small amount of current which may reach relay F from transformer E produces a torque in the opposite direction to the normal, so that this small leakagecurrent is on the side of safety. In fact, when a train is directly across the terminals of transformer E so that no current from that transformer'is passing to relay F a very small leakage-current reaches the relay F from transformer E which tends to actually drive it toward open-circuit position. Thus, although this leakage-current is ordinarily too small to be of any appreciable effect, it is of some assistance in preventing the relay from sticking in closed-circuit position when shunted by a train.

By comparing Figs. 1 and 2, it will be seen that while the distance between adjacent transformers of the same frequency in Fig. 1 is only three times the distance between each transformer and its relay, the

ratio of these distances'in Fig.2. is four to one, so that the arrangement of Fig. 2

with only two frequencies reduces the proportionate amount of current that flows through both transformer secondaries in series as compared with three frequencies in the arrangement ofFig. 1, or looked at another way, each relay in- Fig. l is a block away from its own transformer, and only twice that distance from another transformer, which tends to send a reverse currentthrough it; while in F ig'. 2 each relay is three times as far away from the nearest transformer'that tends to send areverse current through it, as it is from its own transformer. In fact, by the arrangement of Fi 2, the same efiect as regards this leakagecurrent is obtained as would be obtained by" using four frequencies, in Fig. 1; While three frequenc1es,'w1th the arrangement of Fig. 2, would give the same effect as regards leakage-current, as siX frequencies arranged as in Fig. 1,that is, a wholly negligible effect. Two frequencies, however, if arranged as in Fig. 2, are sufficient for a commercially efficient system.

t will be noted that in the arrangement of Fig. 2, the transformers and the connections across the rallsbetween them formwlth the rails a pair of closed trackcircuits between each two transformers, each transformer being common to two adjacent track circuits, and that each track circult has an independent set of relay contacts included in'a'sigrial-controlling circuit and operating to put at danger the signal guardlng the portion of track over which the track circuit extends upon a failure, from any cause, of current at the far end of the track circuit from the transformer at the other end. The arrangement of Fig. 2 is notthe only modification of Fig. 1,which may be made in order to improve its efiiciency. It is, he erer, a particularly advantageous arrangement for long blocks since each relay is only halfa blo'clraway from its transformer, so that a lowvoltagemay be used 'for the signal circuits in spite of the high impedance of therails. Other modifications will readily occur to those skilled in the art; Furthermore, although I have illustrated my invention with one only one track arrangedifor trains going in one (llIBCtlOII, is equally applicable to any-number of tracks, and for trains going in one orboth directions? Consequently, I do notdesire to limit myself to,

the particular construction and arrangement of parts here shown, but aim in the appended claims to cover all modifications which are within the scopeof my invention.

hat I claim as new, and desire to so cure by Letters" Patent of the United States,

7 i I V l In combination with an-elec'tric railway having both rails conductive'ly continuous foryall currents, a plurality of sourcesjof current connected atintervals .ac'ross'the rails, the current from adjacent sources differing in character. from each other and from the power-current, track-relaysconnected across the rails each'responsivefto current of one character and not to thatof another, and signals controlled by said relays. 3 .7

2. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of high frequency alternating -'current connected at intervals across the rails, the currents from adjacentsources differing in character, track-relays connected across the rails each 'responsiveto current of'one character and not to that of another, and signals controlled bysaid relays. 3. In combination with an electricrailway having both rails conductivelycontinuous for all currents, a plurality of sources of 1 alternating-current connected at intervalsacross therails, adjacent sources being of di'fierent frequency, track-relays connected across the rails each responslve to alternating-current of only one frequ'ency,and signus controlled by said relays.

l. In combination with an electricrailway having both rails 'conductively continuous 1 across the rai'ls'a distance apart, a block signal for. the'portion of trackbetween said sources, and signal-controlling means'connected 'across therails at a point between said sources and arrangedto putsaid signal either of said sources. r

at danger upon a failure of current from 6." In combination'withan electric railway having ..bothrails conductively continuous for all currentsftwo sources of alternating- '-currents of differentfrequencies connected across the railsha distance apart, two relays connectedlacross the rails at a point betweensaid sourceseach responsive to one frequency only, and a signal controlled by the joint action o f. said relays.

' 1'25 7. In'combin'ation with an electric rai-lway having both rails conductively'continu- Y ;.ous fo'r all currents. two sources of alternating-currents of different frequencies con;- nected across the ralls' a distance apart, two

relays connected across the rails at a point between said sources each responsive to one frequency only, a signal, and a controlling circuit therefor including the contacts of both relays in series.

8. In combination with an electric railway having both rails conductively continuous for all currents, two sourcesof current of different character connected across the rails a distance apart, two relays connected across the rails at a point between said sources each responsive to current of one character and not to that of another, and a signal controlled by the joint action of said relays.

9. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of current connected at intervals across the rails, the currents from adjacent sources differing in character from each other and from the power-current, track-relays connected across the rails each responsive to current of one character and not to that of another, and signals each controlled by the joint action .of a plurality of relays.

10. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of alternating-current connected at intervals across the rails, adjacent sources being of different frequency, track-relays connected across the rails each responsive to alternating-current of only one frequency, and signals each controlled by the joint action of a plurality of relays.

11. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of current connected at intervals across the rails, the currents from adjacent sources differing in character from each other and from the power-current, track-relays each having two cooperating windings, one con nected across the rails and the other supplied independently of the rail-circuit with current of the same character as that from one of the adjacent sources, and signals con trolled by said relays. v

12. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of current connected at intervals across the rails, the currents from adjacent sources differing in character from each other and from the power-current, track-relays each having two cooperating windings, one connected across the rails and the other supplied independent-ly of the rail circuit with current of the same character as that from. one of the adjacent sources, and signals each controlled bythe joint action of a plurality of relays.

13. In combination with an electric railway having both rails conductively continu- 15. In combination with of alternating-current connected at intervals across the rails, adjacent sources being of different frequency, track relays each having two cooperating windings, one connected across the rails and the other supplied inde pendently of the railcircuit with alternating-current of the same frequency as one of the adjacent sources, and signals controlled by said relays.

let. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of alternating-current connected at intervals across the rails, adjacent sources being of different frequency, track-relays each having two cooperating windings, one con-- nected across the rails and the other supplied independently of the rail-circuit with alternating-current of the same frequency as one of the adjacent sources, and signals each controlled by the joint action of a plurality of said relays. Y

an electric railway having both rails conductively continuous for all currents, two sources of alternating-currents of different frequencies connected across the rails a distance apart, two relays each having one winding connected across the rails at a point between said sources and a second cooperating winding supplied independently of the rail-circuit, the currents in the second windings of the two relays corresponding in frequency respectively to the two sources, and a signal. controlled by the joint action of said relays.

16. In combination with an electric railway having both rails conductively continuous for all currents, a plurality of sources of alternating-current connected across the rails, adjacent sources being of different frequency and each source being oppositely connected relatively to the nearest source of the same frequency, track relays each having one winding connected across the rails and a second cooperating winding supplied independently of the rail-circuit with current of the same frequency as one adjacent source. and signals controlled by said relays.

17 In combination with an electric railway having both rails conductively c0ntinuous for all currents, supply conductors carrying alternating-currents of different frequencies, transformers having their secondaries connected at intervals across the rails and their primaries connected alternately to supply conductors of different frequencies, track-relays each responsive to currents of only one frequency, and signals controlled by said relays.

18. In combination with an electric railway having both rails conductively continu ous for all currents, supply-conductors carrying alternating-currents of different frequencies, transformers having their secous for all currents, a plurality of sourcesondaries connected at intervals across the rails and their primaries connected alternately to supply-conductors of different frequencies, track-relays each having two cooperating windings, one connected across the rails and the other to thesupply conductors, and signals controlled by said relays. 19(111 combination with an electric'raih, way having both rails 'conductively contlnuous for all currents, supply-conductors carrying alternatingcurrents of different frequencies, transformers having their secondaries connected at intervals across the rails and their primaries connected alter- 'nately to supply-conductors of different frequencies, track-relays arranged in pairs at points midway between each twotransforin-c ers,;each having a winding connected across the rails and a second cooperating winding connected to the supply-conductors, the two carrying alternating currents of different frequencies, transformers having their secondaries connected at intervals across the rails and thelr primaries connected alternately to supply-conductors of difierent frequencies and each transformer being oppositely connected relatively to .the nearest transformer connected to the same suj; plyconductors, track-relays each responsive to currentsof only one frequency, and signals controlled by said relays;

21. In combination with an electric railway having its rails connected to form a plurality' of continuous return-conductors for the power-current, a plurality of sources of alternating-current across the track-rails,

adjacent sources being of different frequency, track-relays connected across the rails each responsive to alternating-currents of only one frequency, and signals controlled by said relays.

22. In combination with an electric railway having its rails connected to form a plurality of continuous 'returrrconductors for the power-current, a plurallty of sources of alternating current {connected across the track-rails adjacent sourcesbeing of different frequency, track-relays each having two "cooperating windings, oneconnected across the rails and the other supplied independently'of the rail-circuit with current of the same frequency as one of the adjacent sources, and signals controlled by saidrelays. I

In combination'with an electric railway, a plurality of sources of alternatingcurrent connected across the rails, the rails being 'connectedto form continuous conductors for all currents between saidsources and adjacent sources being of difl'erentfrequency, track-relays connected across the railseach responsive to alternating-currents of only by said relaysi one frequency, and signalscontrolled :24. In combination with an electric railway, pluralityof sources of alternatingcurrent connected across the rails, the rails being connected to form continuous conductorsfor all currents. between said'sources and I adjacent sources being of diifer'ent fre quency, track-relays each having two 006pera-ting windings, oneconnected across the rails and the other supplied independently .of the rail-circuit with 'current of the same frequency as one of the adjacent sources, and

signals controlled by said relays.

25 In combination with an electric railwayfhaving both track rails continuous for the return of'power-current, a plurality of sources of current differing in character fromthe power-current from each other connected to the track-rails at intervals cor responding to the length of the block, and

track relays for the several blocks responslve to current of one character but not to that of another.

26. In combination with an electric railway having both'track-rails conductively continuous for allscurrents, a plurality of sources of current differing in character frorn'the power-current and'froin each other connected across'the track-rails at intervals,

track-relays connected in pairs across the rails approximately mldway between two adjacent sources eachresponsive to current,

of one character and not to that of another, and signals controlled by said relays.

27. In combination with an electric railway having bOth'track rails continuous, a plura llty of sources of alternating-current of different frequencies connected across the track-rails at intervals, track-relays connected in pairs across the rails approximately midwaylbetween two adjacent sources, one relay of each pair being responsive only to the frequency of one adjacent source and, the other relay being responsive only to the frequency of the other ad acent source, and signals controlled by said relays.

28. In a blocksignal system, in combina- "U011 with "a; ra1lw ay havlng bothrails conductively continuous for all currents, signals for the-blocks, signal controlling circuits,

sources of alternating currentconnected a cross the rails at intervalsadjacentsources being of different character and'trackrelays grouped 111 pairs, one pair being placed-be tween each two ad acent s urces, and each relayhavingits contacts included 'inia cir-c cuit controlling the "signal whicl'i guards the 1 portion of track between said ad acent source.

29. Inaa'bloclr signal system, in vcoinbina" tion with a railway having both ra ls- @011 relay and one ductively continuous for all-currents, signals for the blocks, signal controlling circuits, sources of alternating current connected across the rails at intervals corresponding to the length of a block, adjacent sources being of diilerent character and track relays grouped in pairs, one pair being placed between each two adjacent sources and each relay having its contacts included in a circuit controlling the signal which guards the portion of track between said relay and one adjacent source, each of said signals being controlled by two track relays.

30. in a block signal system, in combination witha railway having both rails conductively continuous for all currents, signals for the blocks, signal controlling circuits, sources of alternating current connected across the rails at intervals, adjacent sources being of difierent character and relays grouped in pairs, one pair being placed between each two adjacent sources, each relay having a winding supplied with current from the rails and a second cooperating winding supplied with current independently of the track circuits and each relay having its con tacts included in a circuit controlling the signal which guards the portion of track between said relay and one adjacent source.

31. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, signals for the blocks, signal controlling circuits, sources of alternating current connected across the rails at intervals corresponding to the length of a block, adjacent sources being of different character and relays grouped in pairs, one pair being placed between each two adjacent sources, each relay having a winding supplied with current from the rails and a second cooperating winding supplied with current independently of the track circuits, and each relay having its contacts included in a circuit controlling the signal which guards the portion of track between said relay and one adjacent source, each signal being controlled by two track relays.

32. In combination with a railway having both rails conductively continuous for all currents, a block signal system, comprising signals for the blocks, controlling circuits therefor, sources of alternating current connected across the track rails at intervals, ad-

jacent sources being of difierent character, connections from one rail to the other between adjacent sources, each set of connections forming with the adjacent sources and the rails between them a pair of closed track circuits, each of said sources being common to twoadjacent track circuits, and an ind ependent set of signal controlling contacts for each track circuit, means interposed in said connections and controlling the contacts to cause the contacts for each track cirtween adjacent sources, each set of connections forming with the adjacent sources and the rails between them a pair of closed track circuits, each of said sources being common to two adjacent track circuits, and an independent set of signal controlling contacts for each track circuit, means interposed in said connections and controlling the contacts to cause the said contacts for each track circuit to open a controlling circuit for the signal guarding the portion of track, over which said track circuit extends, upon a failure of current at the far end of said circuit from the source at the other end, each of the signals guarding a length of track corresponding to two track circuits and. controlled by two of said sets of contacts.

34. in combination with a railway having both rails conductively continuous for all currents, a block signal system comprising sources of alternating current connected across the rails at intervals, adjacent sources being of different character, connections from one rail to the other between adjacent sources, each set of connections forming with the adjacent sources and the rails between them pair of closed traclr circuits, each of said sources being common to two adjacent track circuits, signal controlling circuits, a set of contacts, one for each track circuit, included in said signal controlling circuits, each set of contacts being controlled by current in its track circuit from the source for that circuit only, and signals con trolled by the signal controlling circuits.

35. In combination with a railway having both rails eonductively continuous for all currents, a block signal system comprising 1 sources of alternating current connected across the rails at intervals, adjacent sources being of different character connections from one rail to the other between adjacent sources, each set of connections forming with the adjacent sources and the rails between them a pair of closed track circuits, each of said sources being common to two adjacent track circuits, signal controlling circuits, a set of contacts, one for each track circuit, included in said signal controlling circuits, each set of contacts being contr lled bv current in its track circuit from the source for that circuit only and signals controlled by the signal controlling circuits, the controlling circuits forleach signal including two of said sets of contacts.

36. In a block signal system, in combination with a railway having both rails conductively continuous for allcurrents, signals for the blocks, sources of alternating-current connected across the rails j at intervals, adjacent sourcesbeing of difierent character and track relays controlling the signals each having a winding supplied with current from the rails, said relays being arranged in pairs between adjacent sources, and the two relays of each pairbeing' responsiverespectively to currents from the two adjacent sources whereby one relay of each pair is denergized by a car at any point between said relay and one adjacent source and the other relay by a car at any point'between it and the other adjacent source,

37. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources of alternating current connected across the rails at intervals corresponding to the lengths of the blocks, adjacent sources being ofdifferent character, track relays each having, a winding supplied vwith current from the rails, said relaysbeing arrangedinjpairs 1 between adjacent sources, and the tworelays of eachpair being responsive respectively to currents from the two adjacent sources whereby one relay of each pair is dener gized .by a car at any point between said relay and one adjacent source and the other relay by a carat any point between it and v the other adjacent source, and signals for the'blocks each controlled 'by two track relays. v

38. In a blocksignal system, in combinationwith a railwayhaving both rails conductively continuous for allcurrents; signals for the blocks, sources of alternating current connected across the rails at intervals, adjacent sources being of di'flerent character and track relays controlling the signals each havinga winding supplied with currentvfrom the rails, said relays beingof alternating current connected across {the rails at intervals corresponding to the lengths of the blocks, adjacent sources being of different character, track relays each having awinding supplied with, current controlling the signals,

\ from therailS, said relays being arranged in pairs between adjacent sources, eachrela'y being responsive to current from one adjacent source only and the two relays of each ,pair being responsive .to current from the two adjacent sources respectively, whereby 7 one or the other of said relaysis deene'rgized by a car at any point on-the track between 1 said sources, and signals for the blocks each controlled by {two trackfrelays. v 40. Incombination with a railway'having both rails vconductively continuous forfall currents, a block signal system comprising signals for the blocks, sources of alternating current connected across the rails at inter- H vals, adjacent sources being of diii'erentchan acter, and track relays controlling thesig vnals,-a pair of said relays being placed near each. other between adjacent sources, each relay having a winding supplied with curwinding supplied independently of the'tra'ck circuits with currentof such character asto cause the relay to respond to clearfla signal only vwhen the track winding, is supplied rent'f-rom the rails and a second cooperating withcurrent from a certain one of the adj acent sources and the two'relays ofeach pair responding to current from the two sources respectively.

41. Incombination with a railway having both rails conductively continuous for all currents, a block signal system comprising sources of alternating current connected across the rails at intervals, adj a'cent sources being of difi'erent character, track relays apair of said relays being placednear eachother between vadjacent sources, each relayhaving a winding supplied with cujrrentfrom the rails and. a

second cooperating winding supplied independently of the track circuits with current of such character as to cause the relay to respond to clear a signal only when the track winding is supplied with current from qoneiadjacenti source and'the two relays, of

each pair responding to current from the blocks each controlled by two track relays.

42. A railway blocksignal system comprising a railway both track rails of which are COIldUCtlVGlY continuous for all currents, sources of alternating signaling. current connected across the track-rails atfint'er vals,

two-sources respectively, and signals forthe V track relays supplied with signaling current i from the track rails, said relays beinglZO V groupedin pairs and, one pair being'plac'ed between each two adjacent sources, and signals for the blocks controlled by said relays,

each relay controlling the signal which guards the portion'of track betweensaid relay 'and one adjacent source.

vr 43.; A railway block signal systemcomprising a railway both; track rails of iwhich areconductively continuous for all currents, sources of alternatlng current connected across the track rails at intervals correspond ing to the length of a block, track relays grouped in pairs one pair being placed between each two adjacent sources, each relay having a winding supplied with current from the track rails and a second cooperating winding supplied with current independently of the trackcircuits, and signals for the blocks controlled by said relays, each relay controlling the signal which guards the portion of track between such relay and one adjacent source, and each signal being controlled by two track relays.

4A. In combination with a railway having both rails conductively continuous for all currents, a block signal system, comprising signals for the blocks, controlling circuits therefor, sources of alternating current connected across the track rails at intervals, connections from one rail to the other between adjacent sources, each set of connections forming with the adjacent sources and the rails between them a pair of closed track circuits, each of said sources being common to two adjacent track circuits, and an independent set of signal controlling contacts for each track circuit, means interposed in the said connections and controlling the contacts to cause the said contacts for each track circuit to open a controlling circuit for the signal guarding the portion 01 track, over which said track circuit extends, upon a failure of current at the far end of said circuit from the source at the other end.

45. In combination with a railway having both rails conductively continuous for all currents, a block signal system, comprising signals for the blocks, controlling circuits therefor, sources of alternating current connected across the track rails at intervals, connections from one rail to the other be tween adjacent sources, each set of connections forming with the adjacent sources and the rails between them a pair of closed track circuits, each of said sources being common to two adjacent track circuits, and an independent set of signal controlling contacts for each track circuit, means interposed in the said connections and controlling the contacts to cause the said contacts for each track circuit to open a controlling circuit for the signal guarding the portion of track, over which said track circuit extends, upon a failure of current at the far end of said circuit from the source at the other end, each of the signals guarding a length of track corresponding to two track circuits and controlled by two of said sets of contacts.

46. In combination with a railway having both rails conductively continuous for all currents, a block signal system comprising sources of alternating current connected across the rails at intervals, connections from one rail to the other between adjacent sources, each set of connections forming with the adjacent sources and the rails between them, a pair of closed track circuits each of said sources being common to two adjacent track circuits, signal controlling circuits, sets of contacts, one set for each track circuit, included in said signal controlling circuits, each set of contacts being controlled by current in its track circuit from the source for that circuit only, and signals controlled by the signal controlling circuits.

M. In combination with a railway having both rails conductively continuous for all current-s, a block signal system comprising sources of alternating current connected across the rails at intervals, connections from one rail to the other between adjacent sources, each set of connections forming with the adjacent sources and the rails be tween them a pair of closed track circuits, each of said sources being common to two adjacent track circuits, signal controlling circuits, sets of contacts, one set for each track circuit, included in said signal controlling circuits, each set of contacts being controlled by current in its track circuit from the source for that circuit only and signals controlled by the signal controlling circuits, the controlling circuits for each signal includingtwo of said sets of contacts.

4:8. in a block signal system, in combination with a railway having both rails conductively continuous for all currents, signals for the blocks, sources of alternating current connected across the rails at intervals, and track relays controlling the signals each having a winding supplied with current from the rails, said relays being arranged in pairs between adjacent sources, and the two relays of each pair being responsive respectively to currents from the two adjacent sources, whereby one relay of each pair is deenergized by a car at any point between said relay and one adjacent source and the other relay by a car at any point between it and the other adjacent source.

49. In a block signal system, in combination with a railway having both rails con- Vductively continuous for all currents, sources of alternating current connected across the rails at intervals corresponding to the lengths of the blocks, track relays each having a winding supplied with current from the rails, said relays being arranged in pairs between adjacent sources, and the two relays of each pair being responsive respectively to currents from the two "adjacent sources, whereby one relay of each pair is deenergized by a car at any point between said relay and one adjacent source and the other relay by a car at any point between it and the other adjacent source, and signals for the blocks each controlled by two track relays.

50. In a block'signal system, in combina- 1 between adjacent sources, each relay being:

tion with a railway having both rails conductively continuous for all currents, signals for the blocks, sources of alternating current connected across the rails at intervals, and.

track relays controlling the signals each having a winding supplied with current from the rails, said relays. being arranged in pairs between adjacent sources, eachrelay being responsive to the current from one adjacent source only and the two relays of each pair being responsibe to current from the two adjacent sources respectively, whereby one or the other of said relays is denergized by a car at any point onthe track between said sources. I 7

51. In a block signal system, in combination with a railway having both rails con-- ductively continuous for all currents, sources of alternating current connected across the rails at intervals corresponding to the lengths of the blocks, track relays each having a winding supplied with current from the rails, said relays being arranged in pairs my hand [being responsive to currents from the two adjacent sources respectively, whereby one or the other of said relays is de'e'nergized by a car at any point on the track between said sources, and signals for the blocks each con- I trolled by two track relays.

52. In combination, a railway both track rails of which are conductively continuous" for all currents, a plurality of sources of alternating signaling currents connected across the track rails at intervals, two track relays connected across the rails intermediate each two sources, the relays of each pair being responsive respectively to currents from each of the adjacent sources, and railway signals controlled by said relays. a

In witness whereof I have hereunto set this 4th day of August 1906.

LAURENCE A. HAWKINS.

' Witnesses: I M BENJAMIN B. lHU'LL, GnAon M. HANIGAN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner ofvratents. Washington, D. G. 

